The invention relates to power tools, and particularly to a chuck for a power tool driver having a simplified construction for holding a work tool with increased gripping power and reliability.
Power tool drivers, portable and stationary are well known, such as power hand tools, stationary press and milling machines, and other metal and wood working machines. Although twist drills are the most common tools used with such drivers, screw drivers, nut drivers, burrs, mounted grinding stones, and other cutting or abrading work tools may also be used. Since the work tool may have shanks having various diameters or polygonal cross sections, the power driver is provided with a chuck that is adjustable over a relatively wide range. The chuck may be attached to the power driver by a threaded or tapered bore. A wide variety of chucks have been developed in the art. In one common form three, threaded jaws spaced circumferentially 120xc2x0 apart are constrained in angularly disposed passageways in a body. The body is attached onto the drive shaft of a power tool. The chuck typically includes a front sleeve that is pressed to a nut having interior threads. The interior threads mesh with threaded portions of the chuck jaws so that as the front sleeve is rotated, the jaws are caused to either open or close depending on the direction of rotation. The front sleeve is fitted on a rear sleeve so that a bearing or bearing ring must be provided between the nut and the rear sleeve assembly. Because the front sleeve turns, the bearing must necessarily be located near the front of the chuck where direct and other particles, which may damage the bearing, can easily reach the bearing. The gripping force applied by the jaws to the work tool is limited by the small contact area between the mating nut threads and jaw threads so that the gripping torque at the chuck bite is also limited. Because the jaws are threaded, the amount the jaws can be hardened is limited or the threads are made brittle and highly susceptible to breakage. The hardness of the work tool is usually greater than the hardness of the chuck jaws so that the accuracy of the run out of the work tool is also limited. Moreover, since the typical chuck is front sleeve actuated, the work tool is susceptible to loosening in the chuck if the front sleeve bumps anything in operation. This often occurs when working or drilling in corners or other tight places. Perhaps the most difficult problem with prior art chucks occurs in their manufacture and assembly. During manufacture, the jaw passages which are drilled out as bores in the body, typically cannot be bored straight through a solid body, but must be formed as more than one bore with interruptions between the multiple bores. By necessity, the jaws must reciprocate in the bores. If misalignment of the multiple bores occurs, the jaws may not function properly and break. However, the biggest problem occurs during assembly. Because the chuck cannot be tested until the front and rear sleeves are pressed to other parts, they cannot be disassembled without destruction of the chuck beyond reuse. Typically, a completed chuck is tested for run out and is tested for a high/low condition of the nose ends of the jaw, i.e., the nose ends are not flush. Also, if a jaw is placed in the wrong bore the chuck will not operate properly. The entire chuck is typically thrown away if the chuck is defective resulting in enormous material waste. Neither can the chuck be disassembled for repair. Examples of typical chucks are disclosed in U.S. Pat. Nos. 5,125,673, 5,348,318, and 6,015,135. The latter two patents being directed to some of the bearing problems associated with the typical front sleeve actuated chucks.
Accordingly, an object of the present invention is to provide an improved chuck for reliably gripping a work tool while driven by a power tool and machine;
Another object of the present invention is to provide a chuck for gripping a power tool having increased gripping torque and ease of operation.
Another object of the present invention is to provide a chuck having a self-centering operator for opening and closing chuck jaws for more reliable gripping of a power tool for reliable straight run out.
Another object of the present invention is to provide a chuck for gripping a power tool wherein the jaws may be actuated by rear rotation for increased gripping and reliability.
Another object of the present invention is to provide a chuck for gripping a power tool which can be easily assembled and disassembled during manufacture for reducing waste and facilitating repairs after manufacture.
Still another object of the present invention is to provide a chuck for gripping a power tool to provide a chuck which can be tested as a chuck before assembly of the front and rear sleeves.
Still another object of the present invention is to provide a chuck for gripping a power tool having a self-centering jack screw operator for actuating the chuck jaws and providing increased tool gripping torque.
Yet another object of the present invention is to provide a chuck for gripping a power tool which is actuated by rotation of the rear sleeve for increased tool torque and to prevent accidental unloading.
The above objectives are accomplished according to the present invention by a power tool chuck for gripping a work tool comprising a sleeve having a front sleeve and a rear sleeve and a longitudinal chuck axis. A plurality of non-threaded chuck jaws are provided for gripping the work tool. A support body is carried within the sleeve having a plurality of jaw bores for slidably receiving the chuck jaws. A reciprocating traveler is carried in the sleeve, and a rotating operator is carried within the sleeve for reciprocating the traveler along the chuck axis. The chuck jaws have nose ends with bites for gripping the work tool, and the chuck jaws having opposite remote ends carried by the traveler. The operator is affixed with the rear sleeve for rotation with the rear sleeve. In this manner, the chuck bearing is moved to the rear of the chuck. Rotation of the rear sleeve in a first direction moves the traveler causing the nose ends of the chuck jaws to open, and rotation of the rear sleeve in a second direction moves the traveler causing the nose ends to grip the tool. The operator includes an operator base press fitted with the rear sleeve, and a central upstanding operator barrel. Manual rotation of the rear sleeve causes the operator barrel to rotate whereby the traveler reciprocates. Advantageously, the operator barrel is designed as a self-centering jack screw having external operator threads. The traveler includes internal traveler threads which mate with the operator threads on the operator barrel. In one important aspect of the invention, a release space is defined between the support body and an end of the operator barrel. The operator has a jaw release position in which the operator barrel moves into the release space beyond the traveler and engages the support body when the rear sleeve is rotated to open the chuck jaws. A reaction force is created between the operator barrel and support body in the release position causing the traveler to move backwards to produce an initial release of the chuck jaws whereby further rotation of the rear sleeve causes the traveler to continue its backwards travel and open the chuck jaws more fully. A sleeve gap is formed between the front and rear sleeves allowing relative axial movement between the front and rear sleeves. A biasing element is disposed between the front and rear sleeves for biasing the sleeves apart. The sleeve gap decreases as the operator barrel moves into the release space to engage the support body.
Advantageously, the support body includes a support head affixed in the front sleeve and a support shaft extending from the support head and into the rear sleeve. The operator barrel includes a hollow interior in which the support shaft is received so that the operator barrel rotates about the support shaft. The rear sleeve includes a rear opening through,which an end of the support shaft extends to form a protruding shaft end. A locking member engages the protruding shaft end for locking the front sleeve, support shaft, and rear sleeve together. The locking member is removable for disassembly and reassembly. The jaw bores formed in the support head have a bore axis with a prescribed inclination to the chuck axis; and the traveler includes upper inclined bearing surfaces for engaging a first complimentary portion of the jaw end fitting for pushing the jaws through the inclined bores of the support body, and upper bearing surfaces being inclined generally orthogonal to the bore axis for transferring and applying a full upward force from the operator to the jaws in the direction of the bore axis. Lower inclined bearing surfaces are formed on the traveler for bearing against a second complimentary portion of the remote jaw end when the traveler is moved to open the jaws, and the upper and lower inclined bearing surfaces are parallel to each other.
A particular important advantage of the invention is that an integral chuck jaw unit assembly may be provided in a stand-alone form before being pressed into a front and rear sleeve. The integral chuck unit assembly comprises the chuck jaws constrained in the jaw bores of the support body, remote ends of the chuck jaws fitted to the reciprocating traveler, a central operator for reciprocating the traveler, a shaft of the support body extending through the operator, and a locking member engaging the shaft to hold the assembly together without a front and rear sleeve. The integral chuck unit may be assembled and tested as a power tool chuck without a front and rear sleeve, and may be disassembled for repair.
A method for assembling and disassembling a chuck of a power tool which grips a work tool comprises providing a front sleeve and a rear sleeve, and providing an integral chuck jaw unit which includes a support body having a plurality of chuck jaws slidably carried within the support body, and a traveler affixed to the ends of the support jaws, and an operator for reciprocating the traveler. The method includes pressing the support body in the front sleeve; pressing the operator in the rear sleeve, and affixing a removable locking member between the chuck jaw unit and the rear sleeve to complete the assembly wherein the locking member can be removed for disassembling the chuck.